They said the finding, published in the June 5 issue of the New England Journal of Medicine, proves that camels are a source – but perhaps not the only source – of the MERS virus. The illness is contagious, potentially lethal, and has been largely confined to the Middle East so far.

According to the U.S. Centers for Disease Control and Prevention, testing indicates that bats in Saudi Arabia are infected with several strains of MERS-like viruses, and the virus from one bat was identical to the virus from a MERS patient. Bats, therefore, might also play a role in human infection, according to the CDC.

"This [the Saudi study] confirms what we have been suspecting," Marc Siegel, MD, an infectious disease expert and an associate professor of medicine at NYU Langone Medical Center in New York City, told HealthDay. "It's been believed that the source of MERS is the camel, but has really not been proven," until now. "Camels are the Typhoid Mary of MERS," he said. "It is clear, however, that camel-to-human transmission started this thing."